:root {
  --paper: #f6efd9;
  --ink: #2b2118;
  --red: #9b2d2d;
  --gold: #c4a35a;
  --muted: #6b5a48;
  --card: #fffaf0;
  --shadow: 0 10px 30px rgba(60, 40, 20, 0.12);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  min-height: 100%;
  background:
    radial-gradient(circle at 20% 10%, rgba(196, 163, 90, 0.18), transparent 40%),
    var(--paper);
  color: var(--ink);
  font-family: "Iwanami Mincho", "Source Han Serif TC", "Noto Serif TC", "PMingLiU", serif;
}

body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.topbar, .foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 18px;
  background: rgba(255, 250, 240, 0.86);
  border-bottom: 2px solid #d9c7a2;
}

.foot {
  border-bottom: 0;
  border-top: 2px solid #d9c7a2;
  justify-content: center;
  color: var(--muted);
  font-size: 13px;
}

.brand, .top-actions, .lesson-nav, .meaning-box {
  display: flex;
  align-items: center;
  gap: 10px;
}

.brand {
  border: 0;
  background: transparent;
  color: inherit;
  cursor: pointer;
  font: inherit;
  font-weight: 700;
}

.logo-small, .logo-tiny {
  width: 42px;
  height: 42px;
  object-fit: contain;
  background: transparent;
  border: 0;
  border-radius: 0;
}

.logo-tiny { width: 28px; height: 28px; }

.logo-lockup {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0;
}

.logo-cover {
  width: 220px;
  height: auto;
  object-fit: contain;
  background: transparent;
  border: 0;
  border-radius: 0;
  box-shadow: none;
}

.logo-classroom {
  margin: 2px 0 0;
  font-family: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  font-weight: 700;
  letter-spacing: 0.42em;
  font-size: 18px;
  color: #8a09ef;
}

.logo-zh {
  margin: 4px 0 0;
  font-size: 15px;
  letter-spacing: 0.35em;
  color: #8a09ef;
}

.brand-en {
  font-family: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  letter-spacing: 0.08em;
  color: #8a09ef;
}

button {
  font: inherit;
  cursor: pointer;
  border: 1px solid #cbb896;
  background: var(--card);
  color: var(--ink);
  border-radius: 999px;
  padding: 8px 16px;
}

button:hover { border-color: var(--red); color: var(--red); }

.btn-primary {
  background: var(--red);
  color: #fff8e7;
  border-color: var(--red);
  padding: 12px 28px;
  font-size: 18px;
}

.btn-primary:hover { filter: brightness(1.08); color: #fff; }

main { flex: 1; padding: 24px 16px 40px; }

.view { display: none; max-width: 1100px; margin: 0 auto; }
.view.active { display: block; }

.cover {
  text-align: center;
  padding: 48px 16px 24px;
}

.cover h1 {
  font-size: clamp(28px, 5vw, 48px);
  letter-spacing: 0.12em;
  margin: 20px 0 8px;
}

.subtitle { color: var(--muted); font-size: 18px; }
.hint { margin-top: 28px; color: var(--muted); font-size: 14px; }
.muted { color: var(--muted); }

.toc-head { text-align: center; margin-bottom: 20px; }
.toc-head h2 { margin: 0 0 6px; letter-spacing: 0.2em; }

#search {
  width: min(420px, 90%);
  margin-top: 10px;
  padding: 10px 14px;
  border: 1px solid #d9c7a2;
  border-radius: 999px;
  background: var(--card);
  font: inherit;
  text-align: center;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 12px;
}

.card {
  background: var(--card);
  border: 1px solid #e4d3b0;
  border-radius: 14px;
  padding: 10px;
  text-align: center;
  cursor: pointer;
  box-shadow: var(--shadow);
}

.card:hover { border-color: var(--red); transform: translateY(-2px); }

.card img {
  width: 100%;
  aspect-ratio: 1;
  object-fit: cover;
  border-radius: 10px;
  background: #eee8d8;
}

.card .name {
  margin: 8px 0 0;
  font-weight: 700;
  letter-spacing: 0.08em;
}

.lesson {
  max-width: 820px;
  margin: 0 auto;
  text-align: center;
}

.lesson-index { margin: 0; }
.lesson h2 {
  font-size: clamp(32px, 6vw, 56px);
  letter-spacing: 0.18em;
  margin: 6px 0 16px;
  color: var(--red);
}

.lesson figure { margin: 0; }
.lesson img {
  width: min(100%, 720px);
  max-height: 62vh;
  object-fit: contain;
  background: #fff;
  border: 8px solid #fffaf0;
  box-shadow: var(--shadow);
}

.meaning-box {
  flex-direction: column;
  margin: 18px 0;
}

.explain {
  margin: 0;
  font-size: 22px;
  line-height: 1.6;
  background: var(--card);
  border: 1px dashed var(--gold);
  border-radius: 14px;
  padding: 14px 18px;
  width: min(100%, 680px);
}

.hidden { display: none; }

.lesson-nav { justify-content: center; flex-wrap: wrap; }

@media (max-width: 640px) {
  .brand span { display: none; }
  .lesson img { max-height: 48vh; }
  .explain { font-size: 18px; }
}